This proposal addresses a critical problem in medical procedures involving catheters and robot- assisted minimally invasive surgical tooling: the lack of sensitivity at the end-effector. Current catheters and robot-assisted tools provide surgeons with unprecedented access to organs such as the heart. Specialized optical scopes or fibers can also provide a high-quality view of the operating site. However, they do not provide a sense of touch for probing and ablating abnormal tissues, etc. The challenges of producing miniature sensor packages, compatible with in-vivo applications and sufficiently sensitive to measure delicate contact forces, have precluded their application. We propose an approach that involves embedding optical fiber Bragg grating (FBG) sensors into the structure of miniature catheters. The immediate focus is catheters for radiofrequency ablation with accurate force feedback allowing physicians to control tip forces precisely not only to make the lesion size more predictable and controllable, but also to minimize the chance of vascular perforation. In comparison to other sensors, FBG sensors have several advantages: they are chemically inert and physically robust; they are immune to electromagnetic interference, and they have high sensitivity to small strains. Optical multiplexing for multiple sensors located on a single fiber allows an extremely compact device design. In addition, optical fibers can measure infrared emission/absorption properties and provide novel in-situ clinical spectroscopy and other diagnostic tools at the surgeon's fingertips. [unreadable] [unreadable] [unreadable]